(1) Field of the Invention
The present invention relates to a method of incinerating and melting wastes and an apparatus therefor, and particularly to the method and apparatus for incinerating and melting a combustible material, such as a waste of plastic products, paper products, wood, or rubber products and an incombustible material including metal products.
(2) Prior Art
In recent years, the amount of urban wastes generated for disposal has greatly increased due to a change of life style and the migration of the population toward towns and cities.
The most important problem for waste disposal lies in reducing its volume. Another problem lately has been the presence in urban wastes of harmful materials. Because an effluence of harmful materials from the wastes may occur if wastes are buried underground, the tendency has been to incinerate them.
Normally, the ashes of the urban wastes, including those (such as fly ashes) collected by a bag-filter of a collector, were disposed of in such a manner that they were buried underground in reclaimed land or underground during engineering and construction at the time of performing concrete work.
However, these ashes are fine powders which absorb dioxins and include incombustible heavy metals, and therefore it costs substantially to transfer the ashes since there is a great possibility that the ashes may become scattered in the wind when treating and transferring the same. Furthermore, where the ashes are simply buried underground, the harmful materials included in or absorbed in the ashes are washed therefrom due to rain and underground water so as to cause pollution. Therefore, it is required that disposal of the ashes should be carried out carefully.
Recently, laws and rules concerning disposal of urban and industrial wastes are provided, so that it becomes a legal responsibility that the ashes of the wastes must be disposed of via a second treatment after incineration.
As a method of further decreasing the volume of the ashes and resolving the harmful materials so as to prevent the harmful materials from washing out, the ashes are melted. As methods of melting the ashes, a plasma-electric melting, a high-frequency electric melting, and a heat melting by a burner have all been tried.
As mentioned above, it is difficult technically to use the electric furnace since the objects to be incinerated and melted are mostly nonferrous materials. The plasma-electric furnace is very expensive on a large scale and has an increased installation cost.
Therefore, there have been attempts to melt the ashes by means of a conventional heat furnace having a burner which uses a gaseous, liquid or solid fuel. Such a burner type heating means has become popular recently since it has advantages of generation of a high temperature, a high heat efficiency, a low running cost and ease of burning control.
The burner uses LPG, NLG or other fuels, and the air for burning the fuel is supplied by means of an air compressor such as a centrifugal turbine pump or a vane pump and then mixed with the fuel.
This manner of combustion may generate a high temperature which melts the waste ashes, but it is difficult to control generation of a CO gas. Generation of the CO gas means that dioxins, which are closely connected with the CO gas, cannot be controlled.
A conventional waste reduction process is based on the idea that incineration of the wastes is carried out in another process which is quite different from a melting process. As the result, there are further problems in that it is necessary to provide two disposal installations, one for incinerating the wastes and the other for melting the ashes, and the costs for transfer of the wastes and ashes and also the fuel costs become very expensive.
Further, the molten object or slag are fragile after cooling the same and therefore there is no means of disposal except that they should be abandoned at a reclaimed landfill and buried underground.